This invention relates to closed trailers and specifically to an improved design for use with light motor vehicles, providing walk-in access and having a low profile for energy-efficient highway operation.
Various forms of closed trailer for use with light motor vehicles are available which employ a fixed, closed, lockable cover. These include travel trailers and covered trailers for cargo use. Beside being lockable, a fixed cover offers convenience in that it requires no special effort in order to gain access to cargo or to make ready for stationary use after travel, or conversely, to make ready for travel. However, a fixed rigid cover, if high enough to allow walk-in access, results in a large trailer frontal area and, consequently, relatively high aerodynamic drag when in motion, compared with that of a trailer presenting a lower roofline, other things being equal. This results in the requirement of greater towing power and higher energy usage.
As the energy crisis has progressed in the U.S.A., resulting in the need for more fuel-efficient transportation, the automobile has been reduced in both size and power, so that the average motor vehicle is no longer capable of towing a trailer of as great a size and weight as could be towed in the past. To provide acceptable towing vehicle power requirements, rigid lockable covers have been designed which may be lowered for travel and raised to allow walk-in access for loading or other stationary use. These include trailers with mechanisms for raising and lowering a rigid roof section, including roofs which slide vertically over the side walls of the lower body section and trailers having walls which pivot inward from a lower mounting. Such systems are generally applied to sleeping travel trailers. The main disadvantages of such prior art designs are that they require use of parts which are often unique to a particular application and employ relatively complex mechanisms. Opening or closing of such designs generally requires the operator to move to more than one location around the trailer to unlock, unlatch and wind, pump or lift to raise the top. Such designs are therefore relatively costly and/or lack convenience in use.
For smaller trailer applications, where locked closed security of the cargo area is required, rigid covers formed typically of fiberglass reinforced plastic or aluminum, used in conjunction with hinges and counterbalancing spring struts to allow ease of opening from an approximately horizontal position, are available. Such covers, however, are generally limited to light goods or camping gear use, and like drop-roof sleeper trailers, lack the convenience of accessibility when in the lowered for travel position.